To raise the tem­per­ature of one litre of water from 15°C to boiling at 100°C requires a little bit over 355 kilo­joules of energy. An “average” kettle in the UK runs at about 2800 W and in the US at about 1500 W; if we assume that both kettles are 100% effi­cient† then a UK kettle sup­plying 2800 joules per second will take 127 seconds to boil and a US kettle sup­plying 1500 J/s will take 237 seconds, more than a minute and a half longer. This is such a problem that many house­holds in the US still use an old-fashioned stove-top kettle.

I actually did have people ask why I have a stove-top kettle back when I was in Ottawa. I usually said it was just habit (true) and I just didn't have space for another appliance (true) and then later when I wound up with a free electric kettle, I'd tell them that my electric kettle was terrifying (also true), but now I realize I could have said it was all about voltage and seemed *way* more into the science of my tea.

I'm doubting that all of us who use stove-top kettles actually thought about it that way, though. It's just what I was used to. I only switched a few months ago when an electric kettle was all I had while my stuff was in transit. And even if I'd cared, I might not have noticed a difference since water boils around 85°C here instead of 100°C (woo! Altitude helps protect me from burnt tongue!)

... all that said, I almost always boil water in the microwave now. 55s to hot chocolate!